Re: Serial Port COM1 under Linux on IBM ThinkPad 770X

Dirk W. Steinberg (Dirk_Steinberg@bonn.detecon.de)
Fri, 02 Jul 1999 18:39:34 +0200

Alan Cox wrote:
>
> > 0 crw-rw---- 1 root dialout 4, 64 Feb 23 04:42 /dev/ttyS0
> > 0 crw-rw---- 1 root dialout 4, 65 Feb 23 04:42 /dev/ttyS1
> > root@ibmtop:pts/0 ~ # cu -l /dev/ttyS0
> > cu: open (/dev/ttyS0): Permission denied
> > cu: /dev/ttyS0: Line in use
> > zsh: 5731 exit 1 cu -l /dev/ttyS0
> >
> > >From strace cu:
> > open("/dev/ttyS0", O_RDWR|O_NONBLOCK) = -1 EACCES (Permission denied)
> >
> > But this is as superuser (root). How is this possible at all?
>
> cu is setuid to uucp on some systems. Unless you have a deep desire to
> inflict cu on yourself in the name of tradition try playing with minicom.
> If you want to suffer cu then chmod it so its not setuid uucp

root@ibmtop:pts/0 ~ # ll =cu
120 -rwxr-xr-x 1 root root 121156 Apr 21 22:22 /usr/bin/cu*

The cu binary is from Debian 2.2 (potato)

root@ibmtop:pts/0 ~ # dpkg -S =cu
uucp: /usr/bin/cu

As you can see, cu is not suid root. But you were
still right in a sense:

root@ibmtop:pts/0 ~ # strace cu -l /dev/ttyS0 |& grep setuid
setuid(10) = 0

Uid 10 is uucp. I do consider this strange behaviour.

Anyway, I prefer a simple command line tool like cu to a
menu-driven thing like minicom.

All of this still doesn't solve my problem, though.

Thanks for the help, anyway,

Dirk

-- 
Dipl.-Ing. Dirk W. Steinberg
__________________________________________________
Consultant Technologieberatung Informationssysteme
DETECON GmbH,  Oberkasseler Strasse 2,  53227 Bonn
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